Detecting a fraction of a component in a fluid

ABSTRACT

An apparatus, system, and method are disclosed herein. In one embodiment, the apparatus includes a plurality of valves. Each valve of the plurality of valves is associated with a respective production zone of a well. Each valve includes a valve body having a passage and an inflow fluid input through which a formation fluid from the respective production zone associated with the valve is to enter the passage of the valve body. Each valve further includes a sensor located within the valve body to detect a density of the formation fluid. The apparatus further includes a processor programmed to determine a fraction of a subject fluid in the formation fluid based on the density of the formation fluid and a density of the subject fluid.

BACKGROUND

A well may produce fluids with a high percentage of oil, or otherdesired hydrocarbons, when it is first completed. Over time, however,the quantity of undesirable fluids (for example, water or natural gas)in the produced fluids increases. In multi-zone wells, it is possiblethat undesirable fluids are produced from only a few of the zones andthat the quality of the fluids produced from the well could be improvedby limiting or eliminating the fluids produced from those zones. It is achallenge to determine the fraction of undesirable fluids (i.e., the“cut”) in fluids produced from zones in a well to determine which zonesshould be restricted in production to improve the quality of productionfrom the well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a production system.

FIG. 2 is a schematic of a controllable inflow valve.

FIG. 3 is a schematic of a valve with in-line densitometers and flowmeters.

FIG. 4 is a schematic of a valve with a densitometer and a flow meter ina side tube.

FIG. 5 is a schematic of a valve with a densitometer and a flow meter ina side tube with a pressure-holding shroud.

FIG. 6 is a schematic of a controllable inflow valve.

FIG. 7 is a schematic of a controllable inflow valve.

FIG. 8 is a schematic of a controllable inflow valve.

FIG. 9 is a schematic of a controllable inflow valve.

FIG. 10 is a schematic of a controllable inflow valve.

FIG. 11 is a schematic of a controllable inflow valve.

FIG. 12 is a flow chart describing a method for determining a fractionof a subject fluid in a fluid.

FIG. 13 is a flow chart showing a method for controlling a fraction of asubject fluid in fluids produced from a well.

FIG. 14A is a cross-sectional view of a valve or production tubingshowing the use of a plurality of in-line densitometers and flow metersto determine holdup.

FIG. 14B is a cross-sectional view of a valve or production tubingshowing the use of a plurality of densitometers and flow meters insidetubes to determine holdup.

FIG. 14C is a cross-sectional view of a valve or production tubingshowing the use of a plurality of densitometers and flow meters inshrouded side tubes to determine holdup.

FIG. 15 is a graph depicting the fundamental resonance frequencycharacteristics of different materials in production tubingdensitometers.

DETAILED DESCRIPTION

The following detailed description illustrates embodiments of thepresent disclosure. These embodiments are described in sufficient detailto enable a person of ordinary skill in the art to practice theseembodiments without undue experimentation. It should be understood,however, that the embodiments and examples described herein are given byway of illustration only, and not by way of limitation. Varioussubstitutions, modifications, additions, and rearrangements may be madethat remain potential applications of the disclosed techniques.Therefore, the description that follows is not to be taken as limitingon the scope of the appended claims. In particular, an elementassociated with a particular embodiment should not be limited toassociation with that particular embodiment but should be assumed to becapable of association with any embodiment discussed herein.

FIG. 1 is a schematic of a production system. A production system 102includes production tubing 104 that carries hydrocarbons and/or otherproducts from a well 106 to the surface 108. The well 106 includes aborehole 110 that penetrates zones 112 a, 112 b, 112 c, etc. separatedby packers 114 a, 114 b, 114 c, 114 d, etc. Hydrocarbons and/or otherproducts enter the borehole 110 through perforations 116 (only one islabeled). The hydrocarbons enter the production tubing throughrespective controllable inflow valves 118 a, 118 b, 118 c, etc. Acontroller 120 is connected to the valves 118 a, 118 b, 118 c, etc. viacontrol line 122 and controls the degree to which the valves 118 a, 118b, 118 c, etc. are open via the same control line 122. The control line122 may be a hydraulic control line. The controller 120 may be at thesurface, as shown in FIG. 1. The controller 120 may be below the surface108 near or attached to one or more of the valves 118 a-c.

FIG. 2 is a schematic of a controllable inflow valve 202. The valve 202,with various combinations of components described in connection withFIG. 2 as discussed below in connection with FIGS. 6 through 12, isrepresentative of any of the controllable inflow valves 118 a, 118 b,118 c, etc. The valve 202 includes a valve body 204. The valve body 204contains a chamber, which, for the purposes of this disclosure, is amixing chamber and will be referred to herein by the term “mixingchamber 206.” The valve 202 includes an upstream fluid input 208 to themixing chamber 206, an inflow fluid input 210 to the mixing chamber 206,and a fluid output 212 from the mixing chamber 206. The upstream fluidinput 208 may be coupled to the production tubing 104 to receive fluidfrom upstream components (not shown), the inflow fluid input 210receives fluid from the borehole 110 around the valve 202, and the fluidoutput 212 delivers fluid into the production tubing 104 fortransportation to downstream components (not shown) and eventually tothe surface 108. Fluid 216 entering the valve 202 through the upstreamfluid input 208 mixes in the mixing chamber 206 with fluid 213 enteringthe valve through the inflow fluid input 210, to produce output fluid226.

The valve 202 may include an inflow flow meter 214 to measure avolumetric flow rate of the fluid 213 flowing into the inflow fluidinput 210 and to produce an inflow flow meter output 218 representingthe measured volumetric flow rate of the fluid 213 flowing into theinflow fluid input 210. In this context, “to measure” or “measuring” isdefined to receiving raw input from sensors, such as the inflow flowmeter 214 and other similar devices described herein, converting the rawinput from analog to a digital format, if necessary, and processing theresulting digital data as necessary to produce the specified output.

The valve 202 may include an inflow densitometer 220 to measure adensity of the fluid 213 flowing into the inflow fluid input 210 and toproduce an inflow densitometer output 222 representing the measureddensity of the fluid 213 flowing into in the inflow fluid input 210.

Note that, for clarity and ease of reference, the symbol for a flowmeter, such as the inflow flow meter 214, includes a stylizedrepresentation of a flow meter at the bottom of a rectangular box andthe symbol for a densitometer, such as inflow densitometer 220 includesa stylized representation of a densitometer at the bottom of arectangular box.

The valve 202 may include an output densitometer 230 to measure adensity of the fluid 226 flowing out of the fluid output 212 and toproduce an output densitometer output 232 representing the measureddensity of the fluid 226 flowing out of the fluid output 212.

The valve 202 may include an output flow meter 224 to measure avolumetric flow rate of a fluid 226 flowing from the mixing chamber 206out of the fluid output 212 and to produce an output flow meter output228 representing the measured volumetric flow rate of the fluid 226flowing out of the fluid output 212.

The valve 202 may include an upstream densitometer 234 to measure adensity of the fluid 216 flowing into the upstream fluid input 208 andto produce an upstream densitometer output 236 representing the measureddensity of the fluid 216 flowing into the upstream fluid input 208.

The valve 202 may include an upstream flow meter 238 to measure avolumetric flow rate of the fluid 216 flowing into the upstream fluidinput 208 and to produce an upstream flow meter output 240 representingthe measured volumetric flow rate of the fluid 216 flowing into theupstream fluid input 208.

The valve 202 includes a computer 242, which, may be coupled to theinflow flow meter output 218, the inflow densitometer output 222, theoutput flow meter output 228, the output densitometer output 232, theupstream densitometer output 236, and the upstream flow meter output240. The computer 242 is programmed to use a subset of those outputsalong with a density of oil and a density of a subject fluid todetermine a fraction of the subject fluid in a fluid flowing in one ormore of the inflow fluid input 210, upstream fluid input 208, or thefluid output 212.

The inflow flow meter 214, the inflow densitometer 220, the output flowmeter 224, the output densitometer 230, the upstream flow meter 238, andthe upstream densitometer 234 may be attached to the valve body 204.

The subject fluid could be water, could be gas, and/or could be oil. Thesubject fluid may be a mixture of two or more of water, gas, and oil.

The fluid 216 in the upstream fluid input 208 and a fluid 213 in theinflow fluid input 210 are mixed in the mixing chamber 206 to produce inthe fluid output 212 a well-mixed combination of the fluid 216 in theupstream fluid input 208 and the fluid 213 in the inflow fluid input210. The term “well-mixed” is defined to mean that different phases inthe fluid described as “well-mixed” are homogenously distributed in thefluid and move through the production tubing 104 at the same velocity.For example, a well-mixed combination of oil and water would have theoil and water homogenously mixed.

Returning to FIG. 1, an output tubular, such as the production tubing104, is coupled to the fluid output 212. The output flow meter 224 andthe output densitometer 230, are positioned within a well-mixed range124 a, 124 b, 124 c, etc. of the mixing chamber 206 such that the outputflow meter 224 measures the volumetric flow rate of the fluid 226flowing out of the fluid output 212 and the output densitometer 230measures the density of the fluid 226 flowing out of the fluid output212 in the output tubular (i.e., production tubing 104) within awell-mixed range 124 a, 124 b, 124 c, etc. of the mixing chamber 206 inthe respective valve 118 a, 118 b, 118 c, etc. The term “well-mixedrange” is defined to mean the distance over which flowing fluid remainswell-mixed and is typically in a range of 0 to 10 times the internalbore diameter of the fluid output 212. The well-mixed range 124 a, 124b, 124 c, etc. may be outside the respective valve 118 a, 118 b, 118 c,etc., as shown in FIG. 1. The well-mixed range 124 a, 124 b, 124 c, etc.may be inside the respective valve 118 a, 118 b, 118 c, etc. Thewell-mixed range 124 a, 124 b, 124 c, etc. may be partially outside therespective valve 118 a, 118 b, 118 c, etc. and partially inside therespective valve 118 a, 118 b, 118 c. The well-mixed range may be threefeet (0.91 meters). The well-mixed range may be 1 foot (0.30 meters).The well-mixed range may be three inches (7.62 centimeters).

The valve 202 includes a controllable inflow valve 244, shown in FIG. 2,to control the amount of fluid 213 entering the mixing chamber 206through the inflow fluid input 210. The controllable inflow valve 244may be similar to the Interval Control Valve (“ICV”) available fromHalliburton. The controllable inflow valve 244 is controlled by thecomputer 242 by way of control line 246. The controllable inflow valve244 can be commanded to be open, closed, or open by a controllableamount between open and closed. The controllable inflow valve 244 can beopened in 10 increments (i.e., 10 percent open, 20 percent open, 30percent open, 40 percent open, 50 percent open, 60 percent open, 70percent open, 80 percent open, 90 percent open, and 100 percent open).

The inflow flow meter 214, the output flow meter 224, and the upstreamflow meter 238 may include Venturi devices, such as the FLOSTREAM™Venturi flow meters available from Halliburton, that measure flow usingthe Venturi effect. Other types of flow meters, such as those thatdetermine flow rate from the pressure on either side of an orifice, maybe used.

The inflow densitometer 220, the output densitometer 230, and theupstream densitometer 234 may include a vibrating tube densitometer,such as those described in U.S. Pat. No. 9,008,977, entitled DeterminingFluid Density.” which is assigned to the assignee of the instantapplication. Such vibrating tube densitometers use measured vibrationfrequencies of a tubular sample cavity filled with a liquid to determineproperties, including density, of the fluid. More specifically, by usingan excitation source, and measuring the resulting resonant frequency ofthe combined fluid and tube assembly, the total mass, consisting of themass of the tube and the fluid flowing through it, can be calculated asthe mass density of the fluid changes. Therefore, by monitoring theresonant frequencies of the vibrating tube, it is possible to measurethe density of the fluid mass.

FIG. 3 is a schematic of a valve with in-line densitometers and flowmeters. The upstream densitometer 234, the upstream flow meter 238, theoutput densitometer 230, and the output flow meter 224 may be in-linewith the production tubing 104. The inflow flow meter 214, the inflowdensitometer 220, the output flow meter 224, the output densitometer230, the upstream flow meter 238, and the upstream densitometer 234 maybe permanently installed in a zone, or inserted as needed within a zoneusing a wireline, Slickline, or tubing tool, depending on requirementsfrom the operator, cost considerations, and specific conditions of thefield.

The production tubing 104 may act as the tube in a vibrating-tubedensitometer with the packers 114 a, 114 b, 114 c, etc. forming theanchor points for the tube. Such embodiments may not have flow meters. Avibration emitter may be formed from a magnet that may be attached tothe vibrating tube and generates a time-dependent electromagnetic force(EMF) from the magnetic flux change experienced by a magnetic coilinteracting with the moving magnet. Other vibration emitters may includepiezoelectric sources, mechanical hammers/tappers, microexplosions, orthe flow of the fluid itself. Vibration detectors or vibration sensorsthat may be included in the densitometers 220, 230, and 234 may includeaccelerometers, optical sensors (fiber Bragg grating point sensors,reflectometers, Sagnac coils, distributed acoustic sensors, ordistributed strain sensors), piezoelectric or flexoelectric sensors, andelectric strain gauges (resistive or capacitive).

The temperature and pressure within the densitometer may be measuredin-situ in order to provide more accurate calculation of the fluiddensity, and hence water cut. Additional methods to improve thecalculation are using pressure, volume, temperature (PVT) data providedby the operator or by optimizing the excitation signal and sensingsignal pick-up.

Phases that have experienced separation can still be estimated bymeasuring multiphase flow rates using cross-correlation methods. Forexample, by using two densitometers at differing locations andmonitoring their time series of changing density data, the speed atwhich a change in material density occurs can be calculated. By knowingthe density of pure fluid phases, the measured change in density can becorrelated to a change in water cut; by knowing the speed this changepropagated, the flow rate of the changing phase can be estimated aswell.

FIG. 4 is a schematic of a densitometer and a flow meter in a side tube.The valve body 204 may include a main channel 402, which may be part ofor connected to the upstream fluid input 208, the inflow fluid input210, or the fluid output 212. The valve body 204 may include a side tube404 into which a portion 406 of the fluid 408 in the main channel 402 isdiverted. A densitometer 410 may measure a density of the fluid 408 inthe side tube 404. A flow meter 412 may measure a rate of flow of thefluid 406 flowing through the side tube 404 and that rate of flow isused to extrapolate the rate of flow of fluid 408 through the mainchannel 402.

The valve 202 may have a plurality of side tubes 404, each with a flowmeter 412 and densitometer 410, placed at different azimuthal positionsaround the main channel 402 (see e.g., FIGS. 14A-14C discussed below).

FIG. 5 is a schematic of a densitometer and a flow meter in a side tubewith a pressure-holding shroud. The arrangement shown in FIG. 4 mayaugmented by adding a pressure-holding shroud 502 around thedensitometer 410 and the flow meter 412 to keep constant the pressurearound the densitometer 410. The pressure-holding shroud 502 may containa fluid at a pre-determined pressure. The pressure-holding shroud 502may keep constant an acoustic impedance around the input densitometer.

The valve 202 may have a plurality of side tubes 404, each with a flowmeter 412 and a densitometer 410, placed at different azimuthalpositions around the main channel 402 and with all of the side tubescovered by pressure holding shroud 502 (see e.g., FIG. 14C discussedbelow)

Referring to FIGS. 1 and 2, a system may include the production tubing104 penetrating an upper zone, e.g., 112 a, and a lower zone, e.g., 112b, in the well 106. A lower zone valve 118 b has a lower zone inflowfluid input 210 coupled to the lower zone 112 b by which fluids from thelower zone 112 b enter the lower zone valve 118 b. The lower zone valve118 b has a lower zone fluid output 212 by which fluid 226 from thelower zone valve 118 b enters the production tubing 104. The lower zonevalve 118 b has a lower zone control (i.e., controllable inflow valve244) to control the amount of fluid 213 from the lower zone 112 b thatenters the production tubing 104. The lower zone valve 118 b includes alower zone cut computer 242 to measure a fraction of a subject fluid ina fluid 213 flowing into the lower zone inflow fluid input 210.

The system includes an upper zone valve 118 a having a first upper zoneinput 208 (the features shown in FIG. 2 are common to the lower zonevalve 118 b, described above, and the upper zone valve 118 a) coupled tothe lower zone fluid output 212 of the lower zone valve 118 b throughthe production tubing 104. The upper zone valve 118 a includes an upperzone inflow fluid input 210 coupled to the upper zone 112 a by whichfluids from the upper zone 112 a enter the upper zone valve 118 a. Theupper zone valve 118 a has an upper zone fluid output 212 by which fluidfrom the upper zone valve 118 a enters the production tubing 104. Theupper zone valve 118 a has an upper zone control (i.e., controllableinflow valve 244) to control the amount of fluid 213 from the upper zone112 a that enters the production tubing 104. The upper zone valve 118 ahas an upper zone cut computer 242 to measure a fraction of the subjectfluid in a fluid 213 flowing into the upper zone inflow fluid input 210.

The system includes a subject fluid controller 120 (see FIG. 1) coupledto the lower zone control (the controllable inflow valve 244 associatedwith the lower zone valve 118 b) and the upper zone control (thecontrollable inflow valve 244 associated with the upper zone valve 118a) to control the amount of fluid from the lower zone 112 b that entersthe production tubing 104 and amount of fluid from the upper zone 112 athat enters the production tubing 104 based on the fraction of thesubject fluid in a fluid flowing into the lower zone inflow fluid input210 associated with lower zone valve 118 b and the fraction of thesubject fluid in a fluid flowing into the upper zone inflow fluid input210 associated with the upper zone valve 118 a.

The subject fluid controller 120 may be distributed among the upper zonecut computer 242 associated with the upper zone valve 118 a and thelower zone cut computer 242 associated with the lower zone valve 118 b.That is, the decision making regarding the amount of fluid to enter theproduction tubing 104 from the upper zone 112 a and the lower zone 112 bmay be performed partly by software in the upper zone cut computer 242associated with the upper zone valve 118 a and partly by the lower zonecut computer 242 associated with the lower zone valve 118 b. All thedecision making regarding the amount of fluid entering the productiontubing 104 from the upper zone 112 a and from the lower zone 112 b maybe performed by software in the upper zone cut computer 242 associatedwith the upper zone valve 118 a or by the lower zone cut computer 242associated with the lower zone valve 118 b.

FIG. 6 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the output flowmeter 224, the upstream densitometer 234 and the upstream flow meter238. Further, the output densitometer 230 is in a side tube, such asdensitometer 410 inside tube 404. Herein, elements inside tubes areindicated by bars across the top edge of the rectangular boxrepresenting the element.

In the embodiment shown in FIG. 6, the fraction of the subject fluid 213flowing into the inflow fluid input 210 is computed using equation (1)below:

$\Phi_{A} = \frac{\rho_{A} - \rho_{O}}{\rho_{S} - \rho_{O}}$where ϕ_(A) is the calculated fraction of the subject fluid in the fluid213 flowing into the inflow fluid input 210; ρ_(A) is the inflowdensitometer 220 output 222 representing the measured density of thefluid 213 flowing into the inflow fluid input 210; ρ_(o) is the densityof oil, and ρ_(s) is the density of the subject fluid.

Similarly, the fraction of the subject fluid flowing out of the fluidoutput 212 is computed using equation (2) below:

$\Phi_{Output} = \frac{\rho_{Output} - \rho_{O}}{\rho_{S} - \rho_{O}}$where ϕ_(Output) is the calculated fraction of the subject fluid in thefluid 226 flowing out of the fluid output 212; ρ_(Output) is themeasured density 232 of the fluid 226 flowing out of the fluid output212; ρ_(o) is defined above in connection with equation (1), and ρ_(s)is defined above in connection with equation (1).

ϕ_(A) from each controllable intake valve 118 a-c can be used, alongwith the inflow flow meter output 218 representing the measuredvolumetric flow rate of the fluid 213 flowing into the inflow fluidinput 210 from each zone 112 a-c to determine the contribution of eachzone to the fraction of the subject fluid produced from the well 106 atthe surface 108.

FIG. 7 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the upstreamdensitometer 234 and the upstream flow meter 238. The output flow meter224 may be a removable venturi device and the output densitometer 230 isin a side tube. Further, the output flow meter 224 and the outputdensitometer 230 are in a side tube either together, as shown in FIGS.3, 4, and 5, or separately. ϕ_(A) may be calculated using equation (1)and ϕ_(Output) may be calculated using equation (2).

FIG. 8 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the inflowdensitometer 220 and the inflow flow meter 214. The output flow meter224 and the output densitometer 230 are in a side tube either together,as shown in FIGS. 3, 4, and 5, or separately. The upstream flow meter238 and the upstream densitometer 234 are in a side tube eithertogether, as shown in FIGS. 3, 4, and 5, or separately. ϕ_(Output) maybe calculated using equation (2) and ϕ_(A) may be calculated usingequation (3) below:

$\Phi_{A} = \frac{{Q_{Output}\left( {\rho_{Output} - \rho_{O}} \right)} - {Q_{up}\left( {\rho_{up} - \rho_{O}} \right)}}{\left( {Q_{Output} - Q_{up}} \right)\left( {\rho_{S} - \rho_{O}} \right)}$

where ϕ_(A) is defined above in connection with equation (1); Q_(output)is the output flow meter 224 output 228 representing the measuredvolumetric flow rate of the fluid 226 flowing out of the fluid output212; ρ_(Output) is defined above in connection with equation (2); Qup isthe upstream flow meter 238 output 240 representing the measuredvolumetric flow rate of the fluid 216 flowing into the upstream fluidinput 208; ρ_(up) is the upstream densitometer 234 output 236representing the measured density of the fluid 216 flowing into theupstream fluid input 208; ρ_(o) is defined above in connection withequation (1); and ρ_(s) is defined above in connection with equation(1).

FIG. 9 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the output flowmeter 224, the output densitometer, the upstream densitometer 234, andthe upstream flow meter 238. ϕA may be calculated using equation (1).

FIG. 10 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the outputdensitometer 230 and the output flow meter 224. The output flow meter224 may be a removable venturi device and the output densitometer 230 isin a side tube. ϕ_(A) may be calculated using equation (1).

FIG. 11 is a schematic of a controllable inflow valve. The valve 202 maybe a version of the valve 202 shown in FIG. 2 without the upstreamdensitometer 234, the upstream flow meter 238, the inflow densitometer220, and the inflow flow meter 214. The output flow meter 224 and theoutput densitometer 230 may be in a side tube either together, as shownin FIGS. 3, 4, and 5, or separately. ϕ_(Output) may be calculated usingequation (2).

ϕ_(A) from each controllable intake valve 118 a-c in any of theconfigurations shown in FIGS. 6-11 can be used, along with the inflowflow meter output 218 representing the measured volumetric flow rate ofthe fluid 213 flowing into the inflow fluid input 210 from each zone 112a-c to determine the contribution of each zone to the fraction of thesubject fluid produced from the well 106 at the surface 108.

ϕ_(Output) from each controllable intake valve 118 a-c in any of theconfigurations shown in FIGS. 6-8, 10 and 12 can be used, along with theoutput flow meter output 228 representing the measured volumetric flowrate of the fluid 226 flowing out of the fluid output 212 from each zone112 a-c to determine the contribution of each zone to the fraction ofthe subject fluid produced from the well 106 at the surface 108.

Note that if a zone is not producing, there is no need to measure thefraction of subject fluid produced from the non-producing zone. Forexample, if zone 112 b in FIG. 1 is not producing the contribution ofzones 112 b and 112 a to the fraction of the subject fluid can bedetermined at zone 112 a.

FIG. 12 is a flow chart describing a method for determining a fractionof a subject fluid in a fluid. The method includes measuring a propertyof a fluid flowing through one of a plurality of passages in a valve(block 1202). The method further includes determining a fraction of asubject fluid in a fluid flowing through into the one of the pluralityof passages using a density of oil, a density of the subject fluid, andthe measured property (block 1204).

The density of oil may be determined from oil produced from a well 106in which the valve 202 is installed when the well 106 first beginsproducing oil.

The technique described herein allows the determination of the fractionof the subject fluid from 0 percent to 100 percent in both vertical andhorizontal wells.

Examples of Use

FIG. 13 is a flow chart showing a method for controlling a fraction of asubject fluid in fluids produced from a well. The valve 202 is useful inthe following scenario. When the well 106 is first drilled andcompleted, a sample is taken of the product from the well 106 (block1302). The sample is analyzed to determine the fraction of the subjectfluid (e.g., water cut) in the product and the density of the oil in theproduct (block 1304). Additional samples of the same type are taken overtime and the fraction of the subject fluid is monitored (block 1306).When the fraction of subject fluid reaches a threshold (block 1308),e.g., such that producing from the well is becoming less profitable(note that if the fraction of subject fluid has not reached thethreshold (“N” branch from block 1308) processing returns to block1306), it may be desirable to reduce the amount of fluids produced froma given zone 112 a, 112 b, 112 c, etc. to improve the quality ofproduction from the well 106 (“Y” branch from block 1308. To do this,the following procedure is performed.

Respective fractions of a subject fluid in respective fluids (i.e.,fluid 213 for all or a subset of the valves 118 a, 118 b, 118 c, etc.)flowing into a plurality of valves 118 a, 118 b, 118 c, etc. aremeasured (block 1310). Each of the plurality of valves 118 a, 118 b, 118c, etc. controls an amount of respective fluid that flows into aproduction tubing 104 from a respective zone 112 a, 112 b, 112 c, etc.in the well 106. The measured fraction of the subject fluid in the fluidflowing into the production tubing 104 from a one of the plurality ofvalves 118 a, 118 b, 118 c, etc. is determined to be greater than athreshold (block 1312). The one of the plurality of valves 118 a, 118 b,118 c, etc. is adjusted to change the amount of respective fluid thatflows into the production tubing 104 from the respective zone in thewell 112 a, 112 b, 112 c, etc. (block 1314) and processing returns toblock 1306.

In another use, the valve 202 is useful in performing the processesdescribed in U.S. Pat. No. 9,388,686, entitled “Maximizing HydrocarbonProduction While Controlling Phase Behavior or Precipitation ofReservoir Impairing Liquids or Solids” (the '686 patent), which isassigned to the assignee of the instant application. The valve 202 andthe processing described above can be used to detect when the gascontent of the fluid 213 entering the valve 202 through the inflow fluidinput 210 is reaching the bubble point or when the content of anothermaterial in the fluid 213 entering the valve 202 through the inflowfluid input 210 reaches a point where it threatens to disrupt productionfrom the well. The controllable inflow valve 244 can then be adjustedper the procedures described in the '686 patent.

FIG. 14A is a cross-sectional view of a valve or production tubingshowing the use of a plurality of in-line densitometers and flow metersto determine holdup. FIG. 14B is a cross-sectional view of a valve orproduction tubing showing the use of a plurality of densitometers andflow meters in side tubes to determine holdup. FIG. 14C is across-sectional view of a valve or production tubing showing the use ofa plurality of densitometers and flow meters in shrouded side tubes todetermine holdup. In another use, the valve 202 is useful in determining“holdup,” which is the relative volume of different phases (i.e., oil,water, gas) in the production tubing 104. Holdup is useful to knowbecause the phases may move through the production tubing 104 atdifferent speeds which might change the cut of each of the phases at thesurface 108 compared to that at the depth of the zones 112 a, 112 b, 112c, etc. Typically, a water holdup measurement in the well-mixed rangewill give the water cut at that location.

A set of in-line densitometers and flow meters 1402 (only one islabeled), similar to the output flow meter 224 and the outputdensitometer 230 illustrated in FIG. 3, may be distributed around theinner perimeter of the production tubing 104, as shown in FIG. 14A. Thedensity and flow measurements produced from the in-line densitometersand flow meters 1402 can be used to determine holdup.

A set of side tubes containing densitometers and flow meters 1404 (onlyone is labeled), similar to the side tubes 404, densitometers 410, andflow meters 412 illustrated in FIG. 4, may be distributed around theouter perimeter of the production tubing 104, as shown in FIG. 14B. Thedensity and flow measurements produced from the side tubes containingdensitometers and flow meters 1404 can be used to determine holdup.

The set of side tubes containing densitometers and flow meters 1404 maybe shielded by a shroud 1406 similar to the shroud 502 illustrated inFIG. 5. The density and flow measurements produced from the side tubescontaining densitometers and flow meters 1404 can be used to determineholdup.

Theoretical Proof-of-Concept

To verify that the proposed method has a measurable resonance frequency,a preliminary calculation comparing fundamental resonance frequencies inproduction tubing densitometers, as shown in the graph in FIG. 15, wasundertaken. The units of the vertical axis in FIG. 15 are “resonancefrequency” in Hertz (Hz) and the units of the horizontal axis aredensity in grams per cubic centimeter (gm/cm³). In the preliminarysimulation, the outside diameter of the production tubing was taken as4.0 inches (10.16 centimeters (cm)), the inside diameter as 3.5 inches(7.62 cm), and the length as a 1 meter (3.37 feet). Two differentmaterials, mild steel (the solid curve in FIG. 15) and titanium alloy(the dashed curve in FIG. 15), were considered. The results show thatthe resonance frequency using production tubing is in the severalhundred Hz range.

From a sensitivity standpoint, the production line densitometer canperform with good resolution, regardless of tubing orientation. Theproduction tubing densitometer is expected to provide an accuracy ofbetter than +/−0.002 gm/cm³ over a pressure range of 0 pounds per squareinch (PSI) to 20,000 PSI and a temperature range of 75° F. to 350° F.under controlled conditions, giving an estimated resolution of at least0.001 g/cm³. Furthermore, because of the near-linear sensitivity slopein the oil and water density range (0.7-1.1 g/cm³), the density sensorcan be used for 0-100% water cut determination.

In one aspect, an apparatus includes a valve body, a mixing chamberwithin the valve body, a plurality of passages through the valve bodyinto the mixing chamber, and a sensor located within the valve body. Thesensor has a sensor output representing a property of a fluid within thevalve body. The apparatus includes a processor coupled to the sensoroutput. The processor is programmed to use the sensor output, a densityof oil and a density of a subject fluid to determine a fraction of thesubject fluid in a fluid flowing through one of the plurality ofpassages

Implementations may include one or more of the following. The pluralityof passages may include an upstream fluid input, an inflow fluid input,and a fluid output. The sensor may include an inflow densitometer tomeasure a density of the fluid flowing into the inflow fluid input andto produce an inflow densitometer output representing the measureddensity of the fluid in the inflow fluid input. The processor may beprogrammed to compute the fraction of the subject fluid flowing in theinflow fluid input using the inflow densitometer output, the density ofoil and the density of the subject fluid.

The sensor may include an inflow flow meter to measure a volumetric flowrate of a fluid flowing into the inflow fluid input and to produce aninflow flow meter output representing the measured volumetric flow rateof the fluid flowing into the inflow fluid input. The sensor may includean output densitometer to measure a density of the fluid flowing out ofthe fluid output and to produce an output densitometer outputrepresenting the measured density of the fluid flowing out of the fluidoutput and the processor may be programmed to compute the fraction ofthe subject fluid flowing out the fluid output using the outputdensitometer output, the density of oil, and the density of the subjectfluid. The sensor may include an output flow meter to measure avolumetric flow rate of a fluid flowing out the fluid output and toproduce an output flow meter output representing the measured volumetricflow rate of the fluid flowing out of the fluid output.

The sensor may include an upstream densitometer to measure a density ofthe fluid flowing into the upstream fluid input and to produce anupstream densitometer output representing the measured density of thefluid flowing into the upstream fluid input and the processor may beprogrammed to compute the fraction of the subject fluid flowing in theupstream fluid input using the upstream densitometer output, the densityof oil, and the density of the subject fluid. The sensor may include anupstream densitometer to measure a density of the fluid flowing into theupstream fluid input and to produce an upstream densitometer outputrepresenting the measured density of the fluid flowing into the upstreamfluid input, an upstream flow meter to measure a volumetric flow rate ofa fluid flowing into the upstream fluid input and to produce an upstreamflow meter output representing the measured volumetric flow rate of thefluid flowing into the inflow fluid input, an inflow densitometer tomeasure a density of the fluid flowing into the inflow fluid input andto produce an inflow densitometer output representing the measureddensity of the fluid in the inflow fluid input, and an inflow flow meterto measure a volumetric flow rate of a fluid flowing into the inflowfluid input and to produce an inflow flow meter output representing themeasured volumetric flow rate of the fluid flowing into the inflow fluidinput, and the processor may be programmed to compute the fraction ofthe subject fluid flowing in the inflow fluid input using the upstreamdensitometer output, the upstream flow meter output, the inflowdensitometer output, the inflow flow meter output, the density of oiland the density of the subject fluid.

The sensor may include an inflow densitometer to measure a density ofthe fluid flowing into the inflow fluid input and to produce an inflowdensitometer output representing the measured density of the fluid inthe inflow fluid input, an inflow flow meter to measure a volumetricflow rate of a fluid flowing into the inflow fluid input and to producean inflow flow meter output representing the measured volumetric flowrate of the fluid flowing into the inflow fluid input, an outputdensitometer to measure a density of the fluid flowing out of the fluidoutput and to produce an output densitometer output representing themeasured density of the fluid flowing out of the fluid output, and anoutput flow meter to measure a volumetric flow rate of a fluid flowingout the fluid output and to produce an output flow meter outputrepresenting the measured volumetric flow rate of the fluid flowing outof the fluid output, and the processor is programmed to compute thefraction of the subject fluid flowing in the inflow fluid input usingthe inflow densitometer output, the inflow flow meter output, the outputdensitometer output, the output flow meter output, the density of oiland the density of the subject fluid.

The sensor may include an output densitometer to measure a density ofthe fluid flowing out of the fluid output and to produce an outputdensitometer output representing the measured density of the fluidflowing out of the fluid output, and an output flow meter to measure avolumetric flow rate of a fluid flowing out the fluid output and toproduce an output flow meter output representing the measured volumetricflow rate of the fluid flowing out of the fluid output, and theprocessor is programmed to compute the fraction of the subject fluidflowing out the fluid output using the output densitometer output, theoutput flow meter output, the density of oil, and the density of thesubject fluid.

At least part of the sensor may be in a side tube off one of thepassages. The subject fluid may be water. The mixing chamber may producein a fluid output a well-mixed combination of a fluid in an upstreamfluid input and a fluid in an inflow fluid input. The sensor may measurethe volumetric flow rate of the fluid flowing out of the fluid outputand the density of the fluid flowing out of the fluid output within awell-mixed range of the mixing chamber. The apparatus may include acontrollable inflow valve to control an amount of fluid entering themixing chamber through one of the plurality of passages. The sensor mayinclude a Venturi device. The sensor may include a vibrating tubedensitometer. The apparatus may include a pressure-holding shroud aroundthe sensor to keep constant the pressure around the sensor. Thepressure-holding shroud may contain a fluid at a pre-determinedpressure. The pressure-holding shroud may keep constant an acousticimpedance around the sensor.

In one aspect, a system includes a production tubing penetrating anupper zone and a lower zone in a well. The system includes a lower zonevalve having a lower zone input coupled to the lower zone by whichfluids from the lower zone enter the lower zone valve, a lower zoneoutput by which fluid from the lower zone valve enters the productiontubing, a lower zone control to control the amount of fluid from thelower zone valve that enters the production tubing, and a lower zone cutcomputer to measure a fraction of a subject fluid in a fluid flowinginto the lower zone input. The system includes an upper zone valvehaving a first upper zone input coupled to the lower zone output of thelower zone valve through the production tubing, a second upper zoneinput coupled to the upper zone by which fluids from the upper zoneenter the upper zone valve, an upper zone output by which fluid from theupper zone valve enters the production tubing, an upper zone control tocontrol the amount of fluid from the upper zone valve that enters theproduction tubing, and an upper zone cut computer to measure a fractionof the subject fluid in a fluid flowing into the second upper zoneinput. The system includes a subject fluid controller coupled to thelower zone control and the upper zone control to control the amount offluid from the lower zone valve that enters the production tubing andamount of fluid from the upper zone valve that enters the productiontubing based on the fraction of the subject fluid in a fluid flowinginto the lower zone input and the fraction of the subject fluid in afluid flowing into the second upper zone input.

Implementations may include one or more of the following. The subjectfluid controller may be distributed among the upper zone cut computerand the lower zone cut computer. In one aspect, a method includesmeasuring a property of a fluid flowing through one of a plurality ofpassages in a valve. The method includes determining a fraction of asubject fluid in a fluid flowing through the one of the plurality ofpassages using a density of oil, a density of the subject fluid, and themeasure property. Implementations may include one or more of thefollowing. The method may include determining the density of oil fromoil produced from a well in which the valve is installed when the wellfirst begins producing oil. In one aspect, a method includes measuringrespective fractions of a subject fluid in respective fluids flowinginto a plurality of valves, each of the plurality of valves controllingan amount of respective fluid that flows into a production tubing from arespective zone in a well. The method includes determining that themeasured fraction of the subject fluid in the fluid flowing into theproduction tubing from a one of the plurality of valves is greater thana threshold, and, in response, adjusting the one of the plurality ofvalves to reduce the amount of respective fluid that flows into theproduction tubing from the respective zone in the well.

Implementations may include one or more of the following. The method mayinclude taking a sample of fluids produced from the well when the wellis first drilled and completed to determine the density of oil. Themethod may include monitoring the fraction of a sample fluid at thesurface to determine that the fraction has exceeded a threshold. In oneaspect, a method includes receiving fluid from a zone in a well througha valve having a upstream fluid input for receiving fluids from aproduction tubing, an inflow fluid input from the zone, the inflow fluidinput being adjustable to adjust the amount of fluid being received fromthe zone, and a fluid output through which a mixture of the fluidentering the valve through the upstream fluid input and the fluidentering the valve through the inflow fluid input exits the valve andflows into the production tubing. The method includes measuring aproperty of a fluid flowing through one of a plurality of passages in avalve, using the measured property of the fluid to determine that asubject fluid in the fluid entering the inflow fluid input isthreatening to disrupt production from the well, and adjusting theinflow fluid input to reduce the likelihood that the content of thesubject fluid in the fluid entering the inflow fluid input will disruptproduction from the well. Implementations may include one or more of thefollowing.

The subject fluid may be gas. The threatened disruption to productionfrom the well may be gas reaching a bubble point in the fluid enteringthe second fluid input. The operations of the flow diagrams aredescribed with references to the systems/apparatus shown in the blockdiagrams. However, it should be understood that the operations of theflow diagrams could be performed by embodiments of systems and apparatusother than those discussed with reference to the block diagrams, andembodiments discussed with reference to the systems/apparatus couldperform operations different than those discussed with reference to theflow diagrams.

The word “coupled” herein means a direct connection or an indirectconnection.

The text above describes one or more specific embodiments of a broaderinvention. The invention also is carried out in a variety of alternateembodiments and thus is not limited to those described here. Theforegoing description of an embodiment of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

What is claimed is:
 1. An apparatus comprising: a plurality of valves,wherein each valve of the plurality of valves is associated with arespective production zone of a well, wherein each valve comprises: avalve body having a passage; an inflow fluid input through which aformation fluid from the respective production zone is to enter thepassage of the valve body; a sensor located within the valve body,wherein the sensor is to measure a density of the formation fluidflowing into the passage of the valve body; an upstream fluid inputformed by a production tubing, wherein an upstream fluid is to enter thepassage of the valve body through the upstream fluid input; and a fluidoutput formed by the production tubing, wherein a mixed fluid comprisingthe upstream fluid and the formation fluid from the respectiveproduction zone is to exit the passage of the valve body through thefluid output, and wherein a processor is programmed to: determine afirst fraction of a subject fluid in the formation fluid from therespective production zone based on the measured density of theformation fluid and a density of the subject fluid; determine a secondfraction of the subject fluid in the upstream fluid; and determine athird fraction of the subject fluid in the mixed fluid based on thefirst fraction and the second fraction.
 2. The apparatus of claim 1,wherein each valve comprises: an inflow flow meter to measure avolumetric flow rate of the formation fluid flowing into the inflowfluid input.
 3. The apparatus of claim 1, wherein each valve comprises:an output densitometer to measure a density of the mixed fluid flowingout the fluid output, wherein the processor is programmed to determinethe third fraction of the subject fluid in the mixed fluid based on thedensity of the mixed fluid and the density of the subject fluid.
 4. Theapparatus of claim 1, wherein each valve comprises an output flow meterto measure a volumetric flow rate of the mixed fluid flowing out thefluid output.
 5. The apparatus of claim 1, wherein each valve comprises:an upstream densitometer to measure a density of the upstream fluidflowing into the upstream fluid input, wherein the processor is furtherprogrammed to determine the second fraction of the subject fluid in theupstream fluid based on the density of the upstream fluid and thedensity of the subject fluid.
 6. The apparatus of claim 1, wherein eachvalve comprises at least one of: an upstream densitometer to measure adensity of the upstream fluid flowing into the upstream fluid input; anupstream flow meter to measure a volumetric flow rate of the upstreamfluid flowing into the upstream fluid input; and an inflow flow meter tomeasure a volumetric flow rate of the formation fluid flowing into theinflow fluid input, wherein the processor is further programmed todetermine the first fraction of the subject fluid in the formation fluidflowing in the inflow fluid input using at least one of the density ofthe upstream fluid, the volumetric flow rate of the upstream fluid, thedensity of the formation fluid, the volumetric flow rate of theformation fluid and the density of the subject fluid.
 7. The apparatusof claim 1, wherein each valve comprises: an inflow densitometer tomeasure the density of the formation fluid flowing into the inflow fluidinput; an inflow flow meter to measure a volumetric flow rate of theformation fluid flowing into the inflow fluid input; an outputdensitometer to measure a density of the mixed fluid flowing out of thefluid output; and an output flow meter to measure a volumetric flow rateof the mixed fluid flowing out of the fluid output, wherein theprocessor is further programmed to determine the first fraction of thesubject fluid in the formation fluid flowing in the inflow fluid inputusing at least one of the density of the formation fluid, the volumetricflow rate of the formation fluid, the density of the mixed fluid, thevolumetric flow rate of the mixed fluid and the density of the subjectfluid.
 8. The apparatus of claim 1, wherein each valve comprises: anoutput densitometer to measure a density of the mixed fluid flowing outof the fluid output; and an output flow meter to measure a volumetricflow rate of the mixed fluid flowing out of the fluid output, whereinthe processor is further programmed to determine the third fraction ofthe subject fluid in the mixed fluid flowing out of the fluid outputbased on the density of the mixed fluid, the volumetric flow rate of themixed fluid, and the density of the subject fluid.
 9. The apparatus ofclaim 1, wherein the subject fluid is one of a water, an oil, and anatural gas.
 10. The apparatus of claim 1, wherein the upstream fluidmixes with the formation fluid within the passage of the valve body tocreate the mixed fluid, and wherein the sensor measures a volumetricflow rate of the mixed fluid and a density of the mixed fluid.
 11. Theapparatus of claim 1, further comprising: a controllable inflow valve,wherein the processor is further programmed to adjust the controllableinflow valve to control an amount of the formation fluid to enter thepassage of the valve body based on the first fraction of the subjectfluid in the formation fluid.
 12. The apparatus of claim 1, wherein atleast one valve of the plurality of valves further comprises apressure-holding shroud around the sensor.
 13. A system comprising: aproduction tubing penetrating an upper zone and a lower zone in a well;a lower zone valve comprising: a lower zone input coupled to the lowerzone by which formation fluid from the lower zone enters the lower zonevalve; and a lower zone output by which fluid from the lower zone valveenters the production tubing; a lower zone control to control flow of anamount of lower zone formation fluid from the lower zone valve to theproduction tubing; an upper zone valve comprising: an upper zone inputcoupled to the upper zone by which formation fluid from the upper zoneenters the upper zone valve; an upper zone output by which fluid fromthe upper zone valve enters the production tubing; and an upper zonecontrol to control flow of an amount of upper zone formation fluid fromthe upper zone valve to the production tubing; a processor; and amachine-readable medium having program code executable by the processorto cause the processor to: determine a first fraction of a subject fluidin the lower zone formation fluid and a second fraction of the subjectfluid in the upper zone formation fluid; determine a third fraction ofthe subject fluid in a mixed fluid comprising the lower zone formationfluid and the upper zone formation fluid based on the first and secondfractions; determine whether the third fraction exceeds a thresholdvalue; and in response to determining that the third fraction exceedsthe threshold value, adjust at least one of the lower zone control andthe upper zone control based on at least one of the first fraction ofthe subject fluid in the lower zone formation fluid and the secondfraction of the subject fluid in the upper zone formation fluid.
 14. Amethod comprising: receiving, via a first inflow fluid input of a firstvalve, a first formation fluid from a first production zone in asubsurface formation of a well; measuring a density of the firstformation fluid; determining a first fraction of a subject fluid in thefirst formation fluid based on the measured density of the firstformation fluid; receiving, via a second inflow fluid input of a secondvalve, a second formation fluid from a second production zone in thesubsurface formation of the well; determining a second fraction of thesubject fluid in the second formation fluid; determining a thirdfraction of the subject fluid in a mixed fluid comprising the first andsecond formation fluid; determining whether the third fraction exceeds afirst threshold value; in response to determining that the fractionexceeds the first threshold value, selecting at least one of the firstinflow fluid input and the second inflow fluid input based on the firstand second fractions; and adjusting the at least one of the first inflowfluid input and the second inflow fluid input to reduce a flow offormation fluid flowing into a corresponding inflow fluid input.
 15. Themethod of claim 14, further comprising: measuring at least one of atemperature and a pressure of the first formation fluid; based on themeasuring, determining that the subject fluid is reaching a bubblepoint, wherein the subject fluid is a gas; and in response todetermining that the subject fluid is reaching the bubble point,adjusting the first inflow fluid input to reduce a flow of the firstformation fluid into the first inflow fluid input.
 16. The method ofclaim 14, further comprising: measuring a first volumetric flow rate ofthe first formation fluid at the first inflow fluid input of the firstvalve; and measuring a second volumetric flow rate of the secondformation fluid at the second inflow fluid input of the second valve,wherein determining the third fraction comprises determining the thirdfraction based on the first fraction, the second fraction, the firstvolumetric flow rate, and the second volumetric flow rate.
 17. Themethod of claim 14, further comprising: determining whether at least oneof the first fraction and the second fraction exceeds a second thresholdvalue; and in response to determining that the at least one of the firstfraction and the second fraction exceeds the second threshold value,reducing the at least one of the first fraction and the second fractionof the subject fluid by adjusting at least one of the first fluid inflowinput and the second fluid inflow input.